Wireless telecommunications networks employ nodes or access points within a geographic area or space to provide wireless coverage for users. An access point (AP) is typically a physical edge device that allows wireless user devices to access network resources, and is sometimes referred to as a node. Wireless local area networks (WLAN) typically employ existing protocols such as those under IEEE 802.11, which is a specification that defines WLAN data link and physical layers. The 802.11 specification includes a media access control (MAC) sublayer within the data link layer, and two sublayers of the physical layer (PHY)—orthogonal frequency division multiplexing (OFDM) and a direct-sequence spread-spectrum (DSSS) modulation scheme. The Bluetooth specification (IEEE 802.15) uses a frequency-hopping spread spectrum (FHSS) modulation scheme.
The FHSS technique modulates a data signal with a narrow band carrier signal that “hops” in a predictable sequence from frequency to frequency as a function of time over a wide band of frequencies. Interference is reduced because a narrow band interferer affects the spread-spectrum signal only if both are transmitting at the same frequency and at the same time. The transmission frequencies are determined by a spreading (hopping) code. The receiver must be set to the same hopping code and must listen at the incoming signal at the proper time and frequency to receive the signal. OFDM splits a wide frequency band into a number of narrow frequency bands and sends data across the sub-channels. DSSS combines a data signal at the sending station with a higher data rate bit sequence, which often is referred to as a “chip sequence.” A high processing gain increases the signal's resistance to interference.
Various IEEE 802.11 protocols exist, including 802.11a, 802.11b, 802.11g, 802.11e, 802.11i and others. These and other protocols are often referred to as “WiFi,” which is short for wireless fidelity. Other short-range wireless protocols include Hiperlan, which has been adopted by the European Telecommunications Standards Institute (ETSI). Other short range wireless protocols and technologies include Bluetooth (IEEE 802.15.1), ultrasonic, infrared, etc. Overall, creating and implementing networks of short range wireless embodies many difficulties.
The headings provided herein are for convenience only and do not necessarily affect the scope or meaning of the claimed invention.
In the drawings, the same reference numbers and acronyms identify elements or acts with the same or similar functionality for ease of understanding and convenience. To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the FIG. number in which that element is first introduced (e.g., element 204 is first introduced and discussed with respect to FIG. 2).